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Olympiads in Informatics15 Olympiads in Informatics Olympiads OlympiadsVolume 15, 2021 in Informatics in Informatics Volume 15, 2021 Foreword 1 Olympiads in Informatics G. AUDRITO, W. DI LUIGI, L. LAURA, E. MORASSUTTO, D. OSTUNI 15 The Italian Job: Moving (Massively) Online a National Olympiad 3 D. GINAT Self-Generated Figures in Sequence Processing 13 J. HASANOV, H. GADIRLI, A. BAGIYEV On Using Real-Time and Post-Contest Data to Improve the Contest Organization, Tech- nical/Scientific Procedures and Build an Efficient Contestant Preparation Strategy 23 M. MAREŠ Security of Grading Systems 37 L. NIKHÁZY, Á. NOSZÁLY, B. DEÁK Why You Should Know and Not Only Use Sorting Algorithms: Some Beautiful Problems 53 P.S. PANKOV, T.M. IMANALIEV, A.A. KENZHALIEV Automatic Makers as a Source for Olympiad Tasks 75 Z. PLUHÁR Extending Computational Thinking Activities 83 V.D. RISTOVSKA, E. STANKOV, P. SEKULOSKI Teaching and Examination Process of Some University Courses before vs during the 91 Corona Crisis Volume 15, 2021 M.S. TSVETKOVA, V.M. KIRYUKHIN Algorithmic Thinking and New Digital Literacy 105 T. VERHOEFF Look Ma, Backtracking without Recursion 119 REPORTS F. HERNÁNDEZ GONZÁLEZ, J.D. RODRÍGUEZ MORALES, D.A. RIPOLL MÉNDEZ The Cuban Olympiad in Informatics: A New Stage from the DMOJ Online Judge 133 A. LAAKSONEN Reviews of Two Programming Books 143 Ics In Informat IOIIad olymp Ional ISSN 1822-7732 Internat ISSN 1822-7732 INTERNATIONAL OLYMPIAD IN INFORMATICS VILNIUS UNIVERSITY OLYMPIADS IN INFORMATICS Volume 15 2021 Selected papers of the International Conference joint with the XXXIII International Olympiad in Informatics (online) Singapore, 19–25 June, 2021 OLYMPIADS IN INFORMATICS Editor-in-Chief Valentina Dagienė Vilnius University, Lithuania, [email protected] Executive Editor Mile Jovanov Sts. Cyril and Methodius University, Macedonia, [email protected] Technical Editor Tatjana Golubovskaja Vilnius University, Lithuania, [email protected] International Editorial Board Benjamin Burton, University of Queensland, Australia, [email protected] Sébastien Combéfis, Computer Science and IT in Education NPO, Louvain-la-Neuve, Belgium, [email protected] Michal Forišek, Comenius University, Bratislava, Slovakia, [email protected] Gerald Futschek, Vienna University of Technology, Austria, [email protected] Marcin Kubica, Warsaw University, Poland, [email protected] Ville Leppänen, University of Turku, Finland, [email protected] Krassimir Manev, New Bulgarian University, Bulgaria, [email protected] Seiichi Tani, Nihon University, Japan, [email protected] Peter Waker, International Qualification Alliance, South Africa, [email protected] Willem van der Vegt, Windesheim University for Applied Sciences, The Netherlands, [email protected] The journal Olympiads in Informatics is an international open access journal devoted to publishing original research of the highest quality in all aspects of learning and teaching informatics through olympiads and other competitions. https://ioinformatics.org/page/ioi-journal ISSN 1822-7732 (Print) 2335-8955 (Online) © International Olympiad in Informatics, 2021 Vilnius University, 2021 All rights reserved Olympiads in Informatics, 2021 Vol. 15, 1–2 © 2021 IOI, Vilnius University DOI: 10.15388/ioi.2021.00 Foreword IOI, the International Olympiad in Informatics, second year in a row organized by Sin- gapore from June 19th to 28th, 2021, is held online again due to the worldwide spread of COVID-19. A traditional one-day scientific conference is replaced by only virtual presentations of the articles on June 21st. The 15th volume consists of ten research articles, and two reports. Giorgio Audrito, William Di Luigi, Luigi Laura, Edoardo Morassutto, and Dario Ostuni share the experience gained and tools produced during a year of online Olym- piads in Italy, hoping that other countries can benefit from these tools and suggestions for their own Olympiads. The authors provide a list of online resources after the refer- ence list, including GitHub urls of the developed tools. In his article “Self-Generated Figures in Sequence Processing”, David Ginat deals with self-generated figures in algorithmic problem solving. Such figures elicit associa- tions of hidden patterns, whose recognition yields elegant and efficient algorithmic solutions. IOI students have demonstrated constructive utilization of self-generated figures in solving challenging sequence processing tasks. The author believes that this problem-solving heuristic should be elaborated, exemplified, and studied in the teach- ing of algorithmics, at all levels, including the Olympiad level. Jamaladdin Hasanov, Habil Gadirli, and Aydin Bagiyev provide statistical analyses based on the last on-site IOI and share insights on each of them. The sources of the article and results of the work can be found in a public GitHub repository (https:// github.com/ADA-SITE-JML/ioi-grant) Martin Mare presents “Security of Grading Systems” and discusses various at- tacks on grading system security. Several recommendations are summarized in the conclusion part. In their article, “You Should Know and Not Only Use Sorting Algorithms: Some Beautiful Problems”, Laszlo Nikhazy, Aron Noszaly, and Bence Deak present some beautiful tasks where the key to the solution lies in knowing a particular sorting algo- rithm. In some cases, the sorting algorithms are applied as a surprisingly nice idea, for example, in an interactive task or a geometry question. The article of Pavel S. Pankov, Taalaibek M. Imanaliev, and Azret A. Kenzhaliev deals with methods of generating various Olympiad tasks by using evident images of virtual automatic makers. Such tasks are well-understood, have short formulations and are difficult for solving even with initial data of small volume. The authors hope that these tasks would enlarge the scope of tasks involved in the IOI and give ideas for young people to implement in hardware. The article of Zsuzsa Pluhar presents the newest extending activity idea, a challenge game of the Hungarian Bebras initiative. The goal of extension is to create unplugged computational thinking activities based on the Hungarian Bebras competition. Vesna Dimitrievska Ristovska, Emil Stankov, and Petar Sekuloski present a com- parative analysis of the conduction of traditional courses, as opposed to the condi- tions with distance education. The analysis is done from the aspect of the approach to teaching as well as from the aspect of exam conduction and achieved exam results. Presented scenarios for conducting online exams may also be used for conducting online contests in informatics. Marina S. Tsvetkova and Vladimir M. Kiryukhin discuss the concept of algorith- mic thinking in the context of the history of the formation of school informatics, in the competencies of new digital literacy and in the system of developmental education. Tom Verhoeff presents an excellent article, “Look Ma, Backtracking without Re- cursion”, and demonstrates how backtracking can be discovered naturally without us- ing a recursive function nor using a loop with an explicit stack. In the second part of the volume, a national report from Cuba is presented by Francisco Hernandez Gonzalez, José Daniel Rodriguez Morales, and Dovier Antonio Ripoll Mendez. The Cuban Olympiad in Informatics has different stages ranging from the school level to the national contest. In recent years, the competition has been renewed with the use of an instance of the Don Mills Online Judge, an open-source online judge. Finally, Antti Laaksonen overviews two recently published competitive program- ming books: “Algorithmic Thinking” by Daniel Zingaro, and “Competitive Program- ming in Python” by Christoph Dürr and Jill-Jênn Vie. Many thanks to all of those who have assisted with the volume, authors and re- viewers, as well as the Editorial Board of this journal. A lot of work to be done in the process after submitting the first version of papers until the final version ready for printing. We would like to thank the host of this year’s IOI in Singapore for organising the IOI conference online. Editors Olympiads in Informatics, 2021 Vol. 15, 3–12 3 © 2021 IOI, Vilnius University DOI: 10.15388/ioi.2021.01 The Italian Job: Moving (Massively) Online a National Olympiad Giorgio AUDRITO1, William DI LUIGI2, Luigi LAURA2,3, Edoardo MORASSUTTO2, Dario OSTUNI4 1Department of Computer Science, University of Torino, Italy 2Associazione Italiana per l’Informatica ed il Calcolo Automatico 3Uninettuno University, Rome, Italy 4Department of Computer Science, University of Verona, Italy e-mail: [email protected], [email protected], [email protected], [email protected], [email protected] Abstract. The COVID-19 pandemic is having a pervasive effect worldwide, including local, na- tional and international Olympiads in Informatics. Most national Olympiads had to be moved online, a process which poses a number of serious challenges. Help across countries is of uttermost importance in this context, to enable a successful continuation of the IOI during globally hard times. In this paper, we share the experience gained and tools produced during a year of online Olympiads in Italy, hoping that other countries can take profit of these (freely available) tools and suggestions for their own Olympiads. Keywords: team work, programming contest, Olympiads in Informatics, peer education, pro- gramming training. 1. Introduction The Olimpiadi Italiane di Informatica (OII), or Italian Olympiads
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